Collet steel



Patented Mar. 27, 1934 UNITED STATES PATENT OFFICE No Drawing.Application December 11, 1931, Serial No. 580,508

3 Claims.

The object of my invention is to produce an alloy steel particularlysuited to the manufacture of certain machine elements requiring a highdegree of hardness and resilience. For example my improved steel may beused to advantage in the manufacture of collets and feed fingers forautomatic lathes or screw machines.

Taking as an example the manufacture of collets, it is necessary thatthe steel used for this purpose should develop great hardness in thebore of the collet to withstand abrasion from the rod clamped therein.At the same time the steel must be sufficiently resilient to return toits original shape after being released from compression in the spindleheador chuck. It must also withstand the drastic internal stresses setup when the collet is hardened without cracking. This is a difficultrequirement to meet since sharp corners, slots and sudden changes incross section cannot be avoided in the design of collets and since themaximum hardness (and hence the most drastic quenching action) isrequired in the slotted end of the bore where these undesirable featuresare concentrated.

It has heretofore been common practice to use a carbon orcarbon-vanadium tool steel in the manufacture of collets and to waterquench the collet after it has been machined. Steels of this type mayfor example contain:

Percent Carbon .95 to 1.05 Manganese .20 to .30 Silicon .15 to .25Vanadium .15 to .25

' While collets made of this steel and water quenched are in generalsufliciently hard and re silient, it has proved diflicult to produce themore complicated types (particularly those with wide variations in crosssection) without breakage in hardening.

As is well known in the art of heat treating, it is often possible toavoid breakage in hardening by substituting oil for water in thequenching operation. As a rule, however, simple carbon orcarbon-vanadium steels do not develop their maximum hardness whenquenched in oil and I have found that collets made of these steels andoil quenched are not sufficiently hard to be satisfactory in service.Furthermore, the so-called alloy tool steels containing chromium as theprincipal hardening agent and which are commonly oil quenched haveresilient for satisfactory collets. These steels are also considerablymore expensive than simple carbon steels or my improved collet steel.

not proved to be sufllciently 1 have found that if the content ofmanganese in a steel of the carbon or carbon-vanadium type is increasedfrom the usual range, say .20 to 40%. to about .8082, that the resultingsteel when oil quenched will develop the desirable hardness andresiliency of the water quenched carbon steel; and that oil quenchingpractically eliminates the danger of breakage. The compositions which Ihave found most suitable for this purpose lie within the followingrange: v

Percent Carbon .801.50 Manganese .60- .90 Silicon .20- .40 Vanadium .10-.30

It is to be understood that my invention resides in the use of arelatively high content of manganese which permits satisfactory oilhardening of a composition otherwise requiring water quenching. Theabove analysis ranges may therefore be expanded considerably withoutdeparting from the spirit of my invention. As in the case of othersteels. it may be necessary, for example, to vary the carbon contentthrough a considerable range in order to adjust the hardening prop- B0erties of the steel to the section to be hardened. Vanadium in amountsup to .30% may or may not be used in my steel as desired. When present,vanadium exerts its usual cleansing and toughening effect upon thesteel.

Having thus described my invention what I claim as new and desire tosecure by Letters Patent is:

1. An oil hardening tool steel composed of iron, from about .80 itoabout 1.10% of carbon, from about 50% to about .90% of manganese andfrom about 15% to about 25% of vanadium.

2. An oil hardened article made from steel composed of iron. from about30% to about 1.10% of carbon, from about .60% to about .90% of manganeseand from about .15% to about 25% of vanadium.

3. An oil hardened collet made from steel composed of iron, from about.80% to about 1.10% of carbon, from about 50% to about .90% of manganeseand from about 15% to about 25% of vanadium.

DOUGLAS G. ANDERSON.

